<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .box1{
            width: 200px;
            height: 200px;
            background-color: #bbffaa;
            /*float: left;*/
            overflow: hidden;
        }
        .box2{
            width: 200px;
            height: 200px;
            background-color: orange;
            overflow: hidden;
        }
        .box3{
            width: 100px;
            height: 100px;
            background-color: yellow;
            margin-top: 100px;
        }
    </style>
</head>
<body>
    <div class="box1">
        <div class="box3"></div>
    </div>
<!--    <div class="box2">-->

<!--    </div>-->

</body>
</html>